EP1024369B1 - Characterization of a semiconductor-dielectric interface by photocurrent measurements - Google Patents
Characterization of a semiconductor-dielectric interface by photocurrent measurements Download PDFInfo
- Publication number
- EP1024369B1 EP1024369B1 EP99830030A EP99830030A EP1024369B1 EP 1024369 B1 EP1024369 B1 EP 1024369B1 EP 99830030 A EP99830030 A EP 99830030A EP 99830030 A EP99830030 A EP 99830030A EP 1024369 B1 EP1024369 B1 EP 1024369B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- electrode
- electrolyte
- semiconductor
- dielectric
- immersed
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/26—Testing of individual semiconductor devices
- G01R31/265—Contactless testing
- G01R31/2656—Contactless testing using non-ionising electromagnetic radiation, e.g. optical radiation
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/26—Testing of individual semiconductor devices
- G01R31/2648—Characterising semiconductor materials
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L22/00—Testing or measuring during manufacture or treatment; Reliability measurements, i.e. testing of parts without further processing to modify the parts as such; Structural arrangements therefor
- H01L22/10—Measuring as part of the manufacturing process
- H01L22/14—Measuring as part of the manufacturing process for electrical parameters, e.g. resistance, deep-levels, CV, diffusions by electrical means
Definitions
- the present invention relates in general to characterization and mapping techniques of a semiconductor substrate by way of measurements of photocurrents stimulated by scanning the surface of the semiconductor with a laser beam, collected through contacts established through an electrolytic solution.
- the invention relates to characterization techniques of an interface between a semiconductor substrate and a thermally grown or deposited dielectric layer.
- Photocurrent measurements using an electrolyte in contact with the surface of the semiconductor and in which is immersed an electrode of a nonpassivating noble metal such as platinum to establish electrical connection to a biasing circuit are notably used to measure the meanlife of bulk minority carriers of a semiconductor silicon wafer [1] .
- excess carriers are injected by means of a laser beam on the wafer's frontsurface and collected through an inversely biased Schottky contact, realized or on the wafer's backsurface (backside photocurrent mode) or on the same wafer's frontsurface (frontside photocurrent mode).
- an area of the wafer's front is immersed or contacted with a solution suitable to passivate the superficial layers of the wafer and the Schottky contact is biased through a contact established on the wafer's backsurface using an electrolyte with a nonpassivating electrode of a noble metal such as platinum immersed in the electrolytic solution.
- the Schottky contact must be inversely biased in respect to the bulk potential of the wafer which is grounded through one or more ohmic contacts realized on the silicon around the contacted areas or through the electric charges collecting electrolytic solution and eventually through the passivating solution.
- both the passivating solution and the electrolytic solution employed to realize the Schottky contact for collecting photocurrents consists of a diluted fluoridric acid HF solution. Any native or thermal oxide film that may be present on the surface of the semiconductor wafer, is etched away by the HF solution, which also ensures an optimal surface passivation of the silicon [2] .
- the current may be collected on either the wafer's backside or frontside [3] through electrodes of a nonpassivating noble metal, typically of platinum, functionally immersed in the electrolytic solution.
- a nonpassivating noble metal typically of platinum
- the light source for stimulating the photocurrent is a laser beam focused on the wafer's surface (eventually through the film of passivating HF solution) and scanning it by successive lines in order to produce maps of bulk carriers meanlife.
- the US Patent No. 5,130,643 discloses a two-stage method for determining the recombination speed of minority carriers at boundary surfaces between semiconductors and other substances.
- the US Patent No. 4,420,497 discloses a method of detecting and repairing latent defects in a dielectric layer on a semiconductor substrate on which a circuit is to be formed.
- the defects are damaged by the application of an electric field, and are repaired by the selective oxidation or nitridation of the silicon substrate underlying the damaged areas.
- the US Patent No. 4,433,288 provides a method and apparatus for determining the diffusion length of minority carriers in semiconductor materials, using the constant magnitude surface-photovoltage (SPV) method.
- SPV surface-photovoltage
- the laser beam scans the surface of the dielectric layer that covers the semiconductor substrate, in absence of a film of a passivating acid solution because if present it would etch the dielectric oxide and would destroy the interface being examined.
- the photocurrent collected through the Schottky contact that is preferably established on the backside of the wafer of semiconducting silicon through an electrolyte, depends on the bulk minority carriers meanlife as well as on the surface recombination velocity at the semiconductor-dielectric interface, and both parameters may be assessed from a sequence of measurements carried out at different conditions.
- the surface recombination velocity is a parameter that may be extremely useful for characterizing semiconductor-dielectric interfaces, for example an oxide/silicon interface of a gate oxide or tunnel oxide.
- the surface recombination velocity may dramatically vary upon the varying of the surface potential: from a condition of accumulation of majority carriers in respect to the bulk density to a condition of inversion, that is wherein in the silicon at the interface there is a concentration of minority carriers comparable to the concentration of majority carriers in the bulk, as it may occur in presence of electric charges in the oxide at the interface.
- the surface potential cannot be controlled and effects due to the superficial layer density and to eventual electric charges in the oxide cannot be distinguished.
- the possibility to control the potential at the dielectric-semiconductor interface by suitably biasing the gate electrode constituted by the electrolyte, in respect to the semiconductor substrate potential, permits to assess the surface recombination velocity at the interface in function of the voltage applied to the gate electrode besides a charge injection level established by controlling the scanning laser beam.
- the analysis of these data permits to determine both the density of surface states and the electric charges in the dielectric.
- the novel method of the invention Compared to the known methods of measuring the surface recombination velocity, the novel method of the invention has the advantage of discriminating between the effects caused by density of surface states and by eventual electric charges in the dielectric, thus providing an information comparable to that obtained through capacitance-voltage measurements.
- a method based on surface recombination measurements has the advantage of not requiring the realization of capacitors and therefore permits a faster quality control checks of the dielectric/semiconductor interface.
- the wafers may be more accurately mapped through a surface recombination measurements than through capacitance-voltage measurements and an accurate map of the entire wafer may often reveal the reasons for an observed interface degradation.
- the attached figure shows a sectional view of the measurement instrumentation according to the present invention.
- the Schottky contact that collects the photocurrent is realized on the backside of the wafer by biasing the electrolytic HF solution with a platinum electrode Pt ELECTRODE 2 in relation to the potential of the wafer, that is contacted through one or more ohmic contacts, that may be established on the frontside (as schematically shown in the figure) or on the backside of the wafer, preferably around the Schottky contact area.
- a gate electrode on the dielectric layer of Si0 2 present on the frontside is established a gate electrode, an acetic acid solution, biased with a platinum electrode Pt ELECTRODE 1 immersed therein, in relation to the potential of the wafer.
- the electrolytic solution that constitutes the gate electrode on the dielectric may be suitable confined by any of the conventionally used arrangements in this type of instruments and the container of the electrolytic solution has a transparent cover or wall through which and through the thickness of the electrolytic film itself, the laser beam illuminates the wafer covered by the dielectric layer in order to inject excess carriers that are eventually collected through the Schottky contact, through the spatial charge region (SCR) of the Schottky junction realized on the backside of the wafer.
- SCR spatial charge region
- the inverse biasing voltage V2 of the Schottky contact, established on the backside of the silicon wafer, should be sufficiently high to guarantee that according to the inverse I-V characteristic of the junction, the latter be in a saturation condition (to protect from the effects of series resistances) and not excessively high such that the collected current be greater or at least of the same order of magnitude of the junction dark current.
- the bias voltage may be comprised between -5V and -10V (inverse bias).
- the gate electrode constituted by the acetic acid electrolytic solution in contact with the dielectric layer of silicon oxide on the frontside is biased such to move shift from a condition of accumulation to an inversion condition.
- the voltage V1 should not reach values as high as to provoke a significant current leakage through the dielectric, compared to the diffusion current collected by way of the Schottky contact at the backside of the wafer.
- gate voltages ranging within about ⁇ 1.5 V are adequate and produce a negligible current leakage. Of course, thicker oxides would require proportionally increased voltages.
Description
Claims (4)
- A method for characterizing a semiconductor/substrate/dielectric layer interface through measurements of a photocurrent induced in the semiconductor by scanning a certain area of the interface with a laser beam and collected by way of a Schottky contact established by inversely biasing in respect to the potential of the bulk of the semiconductor substrate an electrolyte capable of etching any native or thermal oxide that may exist on the contact area with the semiconductor substrate, characterized in that the surface potential of the semiconductor/dielectric interface is controlled by means of a gate electrode established on the dielectric layer by way of a second electrolyte not aggressive of the dielectric material and biased by an electrode (Pt ELECTRODE 1) immersed in said second electrolyte in respect to the potential of the bulk of said semiconductor substrate.
- The method according to claim 1, characterized in that said first electrolyte (HF) used to constitute a Schottky contact on a certain area of the semiconductor substrate is a diluted HF solution biased by a platinum electrode (Pt ELECTRODE 2) immersed in the electrolyte and said second electrolyte not aggressive of the dielectric material constituting said gate electrode is an acetic acid solution and the biasing electrode immersed in it is of platinum.
- An instrument for measuring a photocurrent collected through a Schottky contact established by inversely biasing an electrolyte in contact with the semiconductor substrate, capable to etch any native or thermal oxide existing on the contact area, in respect to the substrate potential, stimulated by scanning a certain surface of the substrate coated with a dielectric layer with a laser beam, for performing characterization measurements of the semiconductor/dielectric layer interface, characterized in that it comprises means implementing a biasable gate electrode on the dielectric on the area scanned by said laser beam in the form of a transparent layer of electrolyte not aggressive of the dielectric material and an electrode (Pt ELECTRODE 1) of a nonpassivatable metal immersed in said electrolyte.
- The instrument according to claim 3, characterized in that said nonaggressive electrolyte is an acetic acid solution and said metal electrode (Pt ELECTRODE 1) immersed therein is of platinum.
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP99830030A EP1024369B1 (en) | 1999-01-26 | 1999-01-26 | Characterization of a semiconductor-dielectric interface by photocurrent measurements |
DE69921286T DE69921286D1 (en) | 1999-01-26 | 1999-01-26 | Characterization of a semiconductor-dielectric boundary layer using photocurrent measurements |
US09/491,945 US6437592B1 (en) | 1999-01-26 | 2000-01-26 | Characterization of a semiconductor/dielectric interface by photocurrent measurements |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP99830030A EP1024369B1 (en) | 1999-01-26 | 1999-01-26 | Characterization of a semiconductor-dielectric interface by photocurrent measurements |
Publications (2)
Publication Number | Publication Date |
---|---|
EP1024369A1 EP1024369A1 (en) | 2000-08-02 |
EP1024369B1 true EP1024369B1 (en) | 2004-10-20 |
Family
ID=8243241
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP99830030A Expired - Lifetime EP1024369B1 (en) | 1999-01-26 | 1999-01-26 | Characterization of a semiconductor-dielectric interface by photocurrent measurements |
Country Status (3)
Country | Link |
---|---|
US (1) | US6437592B1 (en) |
EP (1) | EP1024369B1 (en) |
DE (1) | DE69921286D1 (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2897197B1 (en) * | 2006-02-03 | 2008-04-18 | Univ Aix Marseill Iii Paul Cezanne | EXTENDED AND ELECTRICALLY MODULAR LIGHT SOURCE, MEASURING DEVICE FOR CHARACTERIZING A SEMICONDUCTOR COMPRISING SUCH A SOURCE |
DE102011051112B4 (en) | 2011-06-05 | 2015-01-08 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Method for measuring the high-voltage degradation of at least one solar cell or a photovoltaic module and its use |
US9153649B2 (en) * | 2012-11-30 | 2015-10-06 | Semiconductor Energy Laboratory Co., Ltd. | Semiconductor device and method for evaluating semiconductor device |
Family Cites Families (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4103228A (en) * | 1977-05-16 | 1978-07-25 | Rca Corp. | Method for determining whether holes in dielectric layers are opened |
US4433288A (en) * | 1981-07-06 | 1984-02-21 | Rca Corporation | Method and apparatus for determining minority carrier diffusion length in semiconductors |
US4420497A (en) * | 1981-08-24 | 1983-12-13 | Fairchild Camera And Instrument Corporation | Method of detecting and repairing latent defects in a semiconductor dielectric layer |
US4473795A (en) * | 1983-02-23 | 1984-09-25 | International Business Machines Corporation | System for resist defect measurement |
DE59006874D1 (en) * | 1989-05-31 | 1994-09-29 | Siemens Ag | Method for determining the recombination rate of minority carriers at interfaces between semiconductors and other substances. |
US5770946A (en) * | 1994-05-11 | 1998-06-23 | Patterson; Joseph M. | Photon assisted sub-tunneling electrical probe, probe tip, and probing method |
US5519334A (en) * | 1994-09-29 | 1996-05-21 | Advanced Micro Devices, Inc. | System and method for measuring charge traps within a dielectric layer formed on a semiconductor wafer |
US6005400A (en) * | 1997-08-22 | 1999-12-21 | Lockheed Martin Energy Research Corporation | High resolution three-dimensional doping profiler |
US5963040A (en) * | 1997-09-24 | 1999-10-05 | Taiwan Semiconductor Manufacturing Co. Ltd. | Method and apparatus for detecting pin-holes in a passivation layer |
-
1999
- 1999-01-26 DE DE69921286T patent/DE69921286D1/en not_active Expired - Lifetime
- 1999-01-26 EP EP99830030A patent/EP1024369B1/en not_active Expired - Lifetime
-
2000
- 2000-01-26 US US09/491,945 patent/US6437592B1/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
DE69921286D1 (en) | 2004-11-25 |
EP1024369A1 (en) | 2000-08-02 |
US6437592B1 (en) | 2002-08-20 |
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